The invention relates to a non-linear optically active (NLO) side chain condensation polymer. For a description of such a polymer reference may be had to U.S. Pat. No. 5,163,100. In this patent document polyurethanes are described which were produced by the condensation polymerization of diols having pendant NLO groups and diisocyanates. Generally, NLO groups are composed of a delocalized .pi. system connected on one side to an electron donating group, namely, a donor group, and on the other to an electron withdrawing group, namely, an acceptor group. The term "Donor-.pi.-Acceptor (D.pi.A) group" is also used.
When a polymeric non-linear optically active material, namely, a polymeric material containing D.pi.A groups, is poled, non-linear polarization occurs under the influence of an external field of force (such as an electric field of force). Non-linear electric polarization may give rise to a number of optically non-linear phenomena, including frequency doubling and Pockels effect. By utilizing these phenomena, it is possible to employ this material in the form of a poled film in optically active waveguiding components such as optical switches, frequency doublers, and so forth, in short, in active optical waveguides.
For all that they display in regard to a high degree of NLO behavior, the abovementioned polymers are not optimally suited to be used in active optical waveguide. The main drawback to the above-described and other known active polymeric waveguides is their loss of signal. In the wavelength area for optical uses (1300-1600 nm) the known polymeric waveguides suffer major losses of signal. Another drawback to the above-described and other known active polymeric waveguides is the fact that the polability still leaves much to be desired. Frequently, during poling only part of the D.pi.A groups is aligned which results in a low initial Pockels coefficient (r33 and r13, which will be elucidated later).